Mobile communications have developed from first generation, analog-based mobile radio systems to second generation digital systems, such as the European Global System for Mobile communications (GSM). Current developments for a third generation of mobile radio communication include the Universal Mobile Telephone communications System (UMTS) and the IMT 2000 system. For simplicity, third generation systems are referred to simply as UMTS. In simple terms, UMTS is “communication to everyone, everywhere,” where communication also includes providing information using different types of media, i.e., multimedia communications.
Second generation mobile/cellular telecommunications networks are typically designed to connect and function with Public Switched Telephone Networks (PSTNs) and Integrated Services Digital Networks (ISDNs). Both of these networks are circuit-switched networks (rather than packet-switched) and handle relatively narrow bandwidth traffic. However, packet-switched networks, such as the Internet, are very much in demand and handle much wider bandwidth traffic than circuit-switched networks. While wireline communication terminals, e.g., personal computers, are capable of utilizing the wider packet-switched network bandwidth, wireless user equipment units (UEs) are at a considerable disadvantage because of the limited bandwidth of the radio/air interface between UEs and packet-switched networks.
UEs are currently limited in the data rates for data communications services such as facsimile, electronic mail, and Internet. The demand is growing for higher data transfer speeds in order the “surf the net” using UEs with fast access to text, images, and sound. Multimedia applications demand high peak bit rates in short bursts, particularly when information is downloaded to the UE. Another challenging multimedia UE application is simultaneous voice and data, e.g., PC application sharing or shared whiteboard. Although this latter type of multimedia application may not require particularly high bit rates, it does require real time, continuous operation because of the voice content. A demanding circuit-switched application (rather than packet-switched as in the Internet application) requiring relatively high bit rates is video conferencing. In order for mobile video conferencing to become practical, the amount of user bandwidth required must be reduced to a minimum without sacrificing image quality.
A UMTS Wideband-Code Division Multiple Access (WCDMA) radio access network provides wireless access at very high data rates and supports enhanced services not realistically attainable with the first and second generation mobile communication systems. WCDMA currently supports 5 MHz-15 MHz, and in the future, promises an even greater bandwidth. In addition to wide bandwidth, WCDMA also improves the quality of service by providing robust operation in fading environments and transparent (“soft”) handoffs between base stations. Multipath fading is used to advantage to enhance quality, i.e., using a RAKE receiver and improved signal processing techniques, contrasted in narrowband systems where fading substantially degrades signal quality.
A UMTS Terrestrial Radio Access Network (UTRAN) responds to radio access service requests by allocating resources needed to support a communication with a UE. The UTRAN includes plural base stations for communicating with UEs over a radio air interface using radio channel resources allocated by a radio network controller connected to the base stations. External network service nodes that interface with external networks, communicate with UEs via the UTRAN. When one of the service nodes requires communication with a UE, the service node requests a radio access “bearer” (RAB) from the UTRAN rather than a specific radio channel resource. A radio access bearer is a logical connection with the UE through the UTRAN and over the radio air interface and corresponds to a single data stream. For example, one radio access bearer may support a speech connection, another bearer may support a video connection, and a third bearer may support a data packet connection. Each radio access bearer is associated with quality of service (QoS) parameters describing how the UTRAN should handle the data stream. Examples of quality of service parameters include data rate, variability of data rate, amount and variability of delay, guaranteed vs. best effort delivery, error rate, etc. Although the term “radio access bearer” is sometimes used for purposes of the following description, the invention applies to any type of “connection,” and is not limited to logical connections like RABs, a particular type of physical connection, etc.
Radio access bearers are dynamically assigned to UTRAN transport and radio channel resources by the UTRAN. The radio access bearer service and the UTRAN isolate the details of transport and radio resource allocation handling as well as details of radio control, e.g., soft handoff. The UTRAN approach is different from traditional approaches where an external network and/or an external network service node is involved in the details of requesting, allocating, and controlling specific radio connections to and from the mobile radio. Instead, the external network service node only needs to request a radio access bearer service over a RAN interface to the UTRAN along with a specific quality of service for a communication to a specific mobile radio. The UTRAN provides the requested service at the requested quality of service (if possible).
Plural radio access bearers may be established and released independently to one UE including bearers from different networks. Moreover, plural radio access bearers, e.g., one carrying circuit-switched information and another carrying packet-switched information, intended for the specific UE may be multiplexed onto the same CDMA channel. Each bearer may have its own transport connection through the UTRAN, or it may be multiplexed with other bearers onto one transport connection.
To initiate a radio access bearer service, a request is transmitted to the UTRAN for communication with a UE. One or more parameters accompany the radio access bearer service request. When establishing each bearer, the UTRAN “maps” or allocates the radio access bearer to physical transport and radio channel resources through the UTRAN and over the radio air interface, respectively. The transport connection between nodes in the UTRAN may be for example an ATM type connection. A radio channel over the air interface includes one or more CDMA spreading codes.
The mapping is based on the one or more parameters associated with the radio access bearer service request. In addition to quality of service parameters, the parameters may also include one or more traffic condition parameters like a congestion level on a common channel, an interference level in the geographic location area in which the UE is currently operating, a distance between the UE and the base station, radio transmit power, the availability of dedicated channel resources, the existence of a dedicated channel to a UE, and other traffic parameters or conditions.
An example Universal Mobile Telecommunications System (UMTS) 10 is shown in FIG. 1. A representative, core network 16, includes a circuit-switched core network (CS CN), shown as box 18, and a packet-switched core network (PS CN), shown as box 20. The circuit-switched core network includes nodes, e.g., Mobile Switching Centers (MSC) 18, Home Locations Register (HLR), Gateway MISC (GMSC), etc., that provide circuit-switched services. The packet-switched core network includes nodes, e.g., Serving GPRS Support Nodes (SGSN) 20, Gateway GPRS Support Node (GGSN), HLR, etc., that are tailored to provide packet-switched services. The CSCN 18 is coupled to an external circuit-switched network 12, such as the Public Switched Telephone Network (PSTN) or the Integrated Services Digital Network (ISDN). The packet-switched core network 20 is coupled to an external packet-switched network 14, such as the Internet.
Each of the core networks 18 and 20 is coupled to a UMTS Terrestrial Radio Access Network (UTRAN) 22 that includes one or more Radio Network Controllers (RNCs) 26. Each RNC is coupled to a plurality of base stations (BSs) 28 and to other RNCs in the UTRAN 22. Each base station 28 corresponds to one access point (one sector or cell) or includes plural access points. Radio communications between one or more base station access points and wireless user equipment unit (UE) 30 are by way of a radio interface. Radio access in this non-limiting example is based on Wideband-CDMA (W-CDMA) with individual radio channels distinguished using spreading codes. Wideband-CDMA provides wide radio bandwidth for multi-media services including packet data applications that have high data rate/bandwidth requirements.
FIG. 2 illustrates an example where a UE has four simultaneous radio access bearers (RABs) with core networks via the UTRAN: one RAB towards the CSCN 18, and three RABs towards the PSCN 20. For simplicity only a single RNC 26 is shown in FIG. 2. In this example, RAB#1 could be used for a speech call, RAB#2 for web browsing, RAB#3 for downloading files with file transfer protocol (FTP), and RAB#4 for sending electronic mail.
UMTS network nodes, such as BSs, RNCs, MSCs, GPRS nodes, etc., may employ a modular and distributed architecture where several processor boards are coupled to a switch. Referring to the generic node 40 in FIG. 3, there may be several processors 44 on each processor board 42. The processors 44 communicate via the switch 46. The switch could be, for example, an ATM-type switch. Further details of such an architecture are described, for example, in commonly-assigned, co-pending application Ser. No. 09/039,453 entitled, “Asynchronous Transfer Mode Platform for Mobile Communications,” filed on Mar. 16, 1998, the disclosure of which is incorporated herein by reference. Each processor 44 may include a self-detecting failure mechanism with one or more hardware detectors and/or software error detection algorithms.
When a connection, such as a radio access bearer (RAB), is established through a network node, a processor is allocated to handle the connection. FIG. 4 shows how four RABs of a UE 30 could be allocated to different processors in an RNC node 26 and a PSCN node 20. For simplicity, only the RABs of one UE 30 are shown, and the base station node is omitted. RAB#1 is handled by processor 1 on processor board C and by CS CN (for which details are omitted). RABs#2 is handled by processor 2 on processor board C and by processor 1 on processor board A. RAB#3 is handled by processor 2 on processor board C and by processor 3 on processor board B. RAB#4 is handled by processor 4 on processor board D and by processor 4 on processor board B.
It is not uncommon for failures of some sort to occur in a node. The whole node or only a part of the node may fail. If the whole node fails, all connections through the node are lost. Consider the example depicted in FIG. 4 where there is a complete failure of the PSCN node 20. As a result, RAB#2, RAB#3, and RAB#4 are lost. However, RAB#1 survives because it is not using the failed PSCN node 20. A partial failure may affect only one device or board, while other devices or boards remain fully operational. An example of a partial failure is when a processor 44 or a processor board 42 crashes or is restarted. In FIG. 4, if processor board C in the RNC 26 fails, RAB#1, RAB#2, and RAB#3 are lost. However, RAB#4 survives because RAB#4 is not supported by the failed processor board C. If processor 3 in board B in the PSCN node 20 experiences a restart, RAB#3 is lost, but other RABs supported by board B survive, including RAB#4 to processor 4.
When a connection is lost in a node due to a failure of some sort, other nodes assigned to support that connection may not detect that the connection has actually been lost. Unless those other nodes are informed, the unreleased connection and associated supporting resources remain reserved for the connection, even though they are not being used. In the example shown in FIG. 5, if processor board C in the RNC 26 fails, RAB#1, RAB#2, and RAB#3 are lost. However, RAB#4 survives because RAB#4 is not using the failed processor board C. The RNC 26 should therefore instruct the CSCN 18 to release RAB#1. The RNC should also instruct the PSCN 20 to release RAB#2 and RAB#3. However, RAB#4 need not be released because it was not affected by the failure. In fact, RAB#4 should not be released if it carries a service independent of the other RABs.
Accordingly, it is desirable to selectively release resources affected by a partial failure in a node, while allowing unaffected node elements, connections, and resources to remain intact and functioning. There are different approaches to achieving these ends. Preferably, those approaches should be easily implemented in existing systems, e.g., using messages already-defined by or consistent with UTRAN standard signaling protocols.
The present invention meets the above-identified objectives. Initially, communication connections are established between an external network and subscriber units (e.g., wireline telephones, wireless UEs, etc.) by way of an access network. The networks may provide wireline service, wireless service, or both. As described earlier, a connection includes any type of logical or physical communications connection that corresponds to a single information stream. A subscriber unit may employ one or plural communication connections. The subscriber unit connection is supported by plural nodes. When a failure is detected in a node, those subscriber unit connections affected by that failure are determined. A failure may include a complete failure in a node, a partial failure in a node, failure in one of several devices in a node, or any other incident that would impact the ability of that node to support a subscriber connection. A message identifying those affected subscriber unit connections is sent to one or more other nodes. Affected subscriber unit connections identified in the message are released. However, those unaffected connections not included in the message are maintained.
In an example embodiment, a list is generated that identifies the subscriber units affected by the detected failure along with the connections affected by the failure. This list is included in the message sent to one or more other nodes supporting a connection of identified subscriber unit connections. In the example context of a radio communications system like UMTS, the node in which the failure is detected may be any one of an external network node, a core network node, a radio access network node such as an RNC or a base station, or a UE.
In another example implementation of the present invention, network addresses, e.g., IP addresses, are assigned to devices in the node. When a subscriber unit connection is established, an address for each device associated with the subscriber unit connection is sent to other nodes. If a failure is detected in one of the devices, a message including the network address of the failed device is sent to one or more other nodes. For nodes containing plural processor boards coupled by a switch, where each processor board includes plural processors, such a message may identify the addresses of the plural processors on a failed board. As a result, the node(s) receiving the message release subscriber unit connections associated with that failed processor board.